Our society has increasingly come to rely upon various devices and processes using wave energy. Some common household examples are electrical systems such as radio, television, and computer circuitry. And some common industrial examples are optical measuring tools, such as laser instruments, although in these the light waves usually are converted to electrical signals at some point.
The most basic attributes of a wave are its amplitude and its frequency. But the timing characteristics of waves, or the "phase," can also be important. The Random House Dictionary of the English Language (1966) gives as its ninth definition of phase: "a particular stage or point of advancement in a cycle; the fractional part of the period through which time has advanced, measured from some arbitrary origin." Waves are cyclical in nature, and once a point in a particular cycle of a particular wave is defined as an origin, it follows that any other point in the same wave, or any point in another coexisting wave can be described with a phase value. Put more simply, we can describe the timing relationship between two distinct waves or between two parts of the same wave as a phase value. Such values can have many uses, such as telling what proportion of a wave cycle has elapsed, or what time has expired since the beginning of a cycle, or what the degree of synchronization, or lack thereof, is between parts of the same wave or of different waves.
The present invention relates to improving the accuracy of measurement of and optionally our control over the attribute of wave phase. Because wave phase is so fundamental to the operation of devices and processes used in homes and in industry, two quite distinct examples of the use of wave phase and the present invention are presented. The first of these is drawn from the field of television, where during signal demodulation one part of a complex signal waveform must be precisely synchronized by another waveform to accurately extract and use color video information. The second example is drawn from the field of laser interferometry, where the change in phase of a measurement signal relative to a reference signal can be used to determine a physical displacement. Of course, many other examples of the use of wave phase are possible, and the examples used herein should not be interpreted as limiting the spirit of the present invention, or the scope of the claims to it which follow.